Nanofiltration (NF), Reverse Osmosis (RO), Electrodialysis (ED), Electrodeionization (EDI) and Membrane Distillation (MD) membrane processes have been used for the treatment of brackish (ground and surface) water, seawater and treated wastewater. During the concentration process, the solubility limits of sparingly soluble salts such as sulfates of calcium, barium, magnesium and strontium; carbonates of calcium, magnesium, barium; and phosphates of calcium, are exceeded, resulting in scale formation on a membrane surface as well as in the system. Membrane scaling results in the loss of permeate flux through the membrane, increases in salt passage through the membrane (except in MD), and increases in pressure drop across membrane elements. All of these factors result in a higher operating cost of running the above-mentioned processes and a loss of water production through these membrane systems.
Antiscalants are successfully used either alone or in conjunction with a pH adjustment (in case of carbonate and phosphate scales) to inhibit scale formation. Most of the commercial antiscalants used e.g. in NF and RO processes are polyacrylates, organo-phosphonates, acrylamide copolymers and/or their blends. Due to increasingly stringent regulations on phosphorous-based materials, phosphorous-free antiscalants are required. Polyacrylate based antiscalants work only with some water chemistries and do not perform well in others, especially those containing iron. Therefore, there is a need for developing phosphorous free antiscalants for NF, RO, ED, EDI and MD processes.